(CNN) — The surviving suspect in the Boston Marathon bombings has told investigators that his older brother, not any international terrorist group, masterminded the deadly attack, a U.S. government source said.
Preliminary interviews with Dzhokhar Tsarnaev indicate the two brothers fit the classification of self-radicalized jihadists, the source said Monday.
Tsarnaev has conveyed to investigators that Tamerlan’s motivation was that of jihadist thought and the idea that Islam is under attack and jihadists need to fight back, the source said.
The government source cautioned that the interviews were preliminary, and that Tsarnaev’s account needs to be checked out and followed up on by investigators.
And a federal law enforcement official told CNN that while investigators have seen nothing yet to indicate the suspects were working with anyone else, plenty of work remains before they can say confidently that no others were involved. That official would not comment on any motive or specifics on what Dzhokhar Tsarnaev has communicated to officials.
Boston commissioner recaps manhunt Suspects called aunt to say ‘I love you’ What FBI knew about suspect #1 in 2011 Questions for Dzhokhar Tsarnaev
As hints of a possible motive continue to emerge, Dzhokhar Tsarnaev remains hospitalized with multiple gunshot wounds.
The 19-year-old has been charged with using and conspiring to use a weapon of mass destruction resulting in death, and one count of malicious destruction of property by means of an explosive device resulting in death. He was heavily sedated and on a ventilator at Beth Israel Deaconess Hospital, but was “alert, mentally competent and lucid” during the brief initial court appearance at his bedside on Monday, U.S. Magistrate Judge Marianne Bowler found.
Read transcript of the hearing
During the hearing, Tsarnaev communicated mostly by nodding his head, though he once answered “no” when Bowler asked him if he could afford a lawyer, according to a transcript of the proceeding. A public defender was appointed to represent him.
Investigators have been asking Tsarnaev whether there are more bombs, explosives caches or weapons beyond those already found by police, and if anyone else was involved in the attacks, a source with direct knowledge of the investigation told CNN. Investigators are going into Tsarnaev’s room every few hours to ask questions in the presence of doctors, the source said.
Federal agents at first questioned Tsarnaev without reading him his Miranda rights, under an exception to the rule invoked when authorities believe there is an imminent public safety threat, a Justice Department official said over the weekend. But by the time of the hospital room proceeding, government sources said he had been read his rights, and Bowler reviewed those with him again Monday.
Bowler scheduled a probable cause hearing for May 30.
Read the charges
Tsarnaev had been shot in the head, neck, legs and one hand, according to an FBI affidavit supporting the charges. He had lost a significant amount of blood and may have hearing loss from two flash-bang devices used to draw him out of the boat, the source said.
It wasn’t clear whether Tsarnaev was wounded during his capture Friday night or in an earlier shootout with police that left his 26-year-old brother dead. Boston Police Commissioner Ed Davis said the brothers, armed with handguns and explosives, apparently were planning another attack before the shootout derailed their efforts.
“I believe that the only reason that someone would have those in their possession was to further attack people and cause more death and destruction,” Davis told CNN Monday.
Among the pieces of evidence collected from Boylston Street during the past week was a tree that Dzhokhar Tsarnaev may have leaned against before the bombing, according to a source who receives regular intelligence briefings on the attack. The source said the tree, located at the site of the second blast, was removed along with the surrounding grate, where the explosive device’s circuit board was found.
Clues about radicalization?
While Tamerlan Tsarnaev apparently became increasingly radical in the past three or four years, according to an analysis of his social media accounts and the recollections of family members, there was no evidence Monday that he had any active association with international jihadist groups.
Tamerlan Tsarnaev, 26, died after a shootout with police early Friday. Dzhokhar Tsarnaev was captured that night, after police found him hiding in a boat in the back yard of a house in the Boston suburb of Watertown, Massachusetts.
Photos: Manhunt for Boston bombers
Photos: Boston celebrates
New evidence photos from Boston
Photos: Nation mourns Boston bomb victims
The Tsarnaev family hails from the Russian republic of Chechnya and fled the brutal wars there in the 1990s. The two brothers were born in Kyrgyzstan; Dzhokhar became a U.S. citizen in 2012, while Tamerlan was a legal U.S. resident.
An FBI official said agents interviewed Tamerlan Tsarnaev in 2011 at the request of the Russian government. The FBI said Russia claimed that he was a follower of radical Islam and that he had changed drastically since 2010.
But the Russian government’s request was vague, a U.S. official and a law enforcement source said Sunday. The lack of specifics limited how much the FBI was able to investigate Tamerlan, the law enforcement official said.
Dead Boston bomb suspect posted video of jihadist, analysis shows
In August 2012, soon after returning from a visit to Russia, the elder Tsarnaev brother created a YouTube channel with links to a number of videos. Two videos under a category labeled “Terrorists” were deleted. It’s not clear when or by whom.
Tamerlan Tsarnaev attended prayers periodically at the Islamic Society of Boston’s mosque in Cambridge, a board member told CNN’s Brian Todd. In a statement issued Monday, the society said he twice interrupted sermons — once in November to express his opposition to celebrating any holiday as un-Islamic, and once in January when he tore into the preacher for citing civil rights leader Martin Luther King.
The second time, the congregation shouted back, “Leave now,” the statement said.
“After the sermon and the congregational prayer ended, a few volunteer leaders of the mosque sat down with the older suspect and gave him a clear choice: either he stops interrupting sermons and remains silent or he would not be welcomed,” it said. “While he continued to attend some of the congregational prayers after the January incident, he neither interrupted another sermon nor did he cause any other disturbances.”